Many localities are experiencing a severe strain in the operation of their municipal wastewater treatment plants, due to increased load from rapid commercial and residential development. Furthermore, the movement of population and industry to unsewered areas has resulted in numerous sewage and waste disposal problems which cannot be resolved by the traditional methods of absorption in the ground. The discharge of untreated wastes from homes can lead to many environmental problems. The discharge of sewage containing potentially disease-causing microorganisms constitutes a hazard to public health. Organic matter in sewage serves as a food source for various microorganisms such as bacteria which uses oxygen to break down the organic matter. Large concentrations of organic matter thus can result in the depletion of dissolved oxygen in receiving streams to such an extent that fish and other aquatic organisms cannot survive.
To protect the environment and public health, sewage treatment is necessary. The two traditional methods of treating home wastes have been the sewer collection system with a central treatment plant, and the individual septic tank with an absorption field. However, the low population density of many rural areas makes sewer construction too expensive for the average rural household. In the rapidly-growing counties and other areas, it is not always possible to keep up with the pace of development by adding to the capacity of existing central sewage treatment plants. Adding to these problems, shallow soil depths, steep slopes, high ground water levels, and impermeable soils in many areas result in septic tank-absorption field failures. Many developing suburban areas in the United States have banned the use of conventional septic tank-absorption field techniques for new housing construction. However, some municipalities have declared a moratorium on the issuance of residential building permits, or will issue such permits only where the individual lot size exceeds a certain minimum square footage, because the existing central sewage treatment plants already are operating at or near capacity. The outright refusal to issue residential building permits, or the issuance of those permits only for larger lots, drives up the prices of existing residences or inflates the cost of new housing in areas having such restrictions imposed by a scarcity of residential wastewater treatment facilities or restricted use of conventional septic tanks.